The goal in this proposal is to use chromosomal rearrangements (CRs) occurring in children with CHDs as signposts to identify novel genes important in cardiac morphogenesis. The underlying hypothesis of this proposal is that we can identify genes critical to normal cardiac development based upon their location in relation to breakpoints of balanced translocations. Further, we hypothesize that other chromosomal changes, such as additions or interstitial deletions will assist in the identification of additional dosage sensitive genes important to cardiac development. The subjects for this study will be children who present to the SCCOR with heart defects and possibly further associated congenital anomalies. We will utilize the fruits of the Human Genome Project as well as novel technology we are developing to characterize the regions involved in the chromosomal aberrations of SCCOR patients. We hypothesize that these regions harbor genes important to normal cardiac development. We will pursue the molecular identification and analysis of cardiac candidate genes such that mutation studies can be the focus of subsequent research studies. Characterization of the candidate genes will include the delineation of their tissue, spatial and temporal expression patterns in mouse and/or Xenopus. We will isolate or identify homologues of these candidate genes in model organisms. Our specific aims include: 1) identification and characterization of CRs in patients with CHD by high-resolution cytogenetics and molecular cytogenetic analysis; 2) development of PCR-based mapping strategies using the human genomic sequence to identify translocation breakpoints (BPs); 3) Characterization of the genomic DNA from normal chromosomes at the BPs in order to identify mechanisms of rearrangement; 4) identification and characterization of genes disrupted or deleted at the translocation BPs as candidates for early cardiac morphogenesis; and 5) determination of whether mutations in the candidate genes are associated with the cardiac defect in other patients with CHD. This represents a unified program of clinical and basic research. It brings together the disciplines of clinical cardiology, clinical genetics, cytogenetics, molecular biology and developmental genetics to examine the influence of genomic variation on the etiology of CHDs in our quest to discover genes involved in fundamental pathways during early cardiogenesis.